title: MR guidance and thermometry of percutaneous laser disc decompression in open MRI: an ex vivo study.
abstract: OBJECTIVE
  To assess the feasibility of guidance and thermometry by open 1.0 T magnetic resonance (MR) imaging during percutaneous laser disc decompression (PLDD).
  
  
  METHODS
  A fluoroscopic proton-density-weighted turbo spin echo sequence was used for positioning a laser fiber and a reference thermosensor within the targeted spinal disc. In 30 lumbar discs from human donors, nonspoiled gradient-echo (GRE) sequences with different echo times (TE) were compared to monitor thermal laser effects (Nd:YAG laser, 1,064 nm). Temperature distribution was visualized in real time on the basis of T1-weighted images and the proton resonance frequency (PRF) technique. Image quality, temperature accuracy, and correlation with macroscopic lesion sizes were analyzed. Image quality was confirmed in healthy volunteers.
  
  
  RESULTS
  MR-guided placement of the laser fiber in the center of the targeted disk was precise. Best overall PLDD results-considering image quality (contrast-to-noise ratio), temperature accuracy (R (2) = 0.96), and correlation between the macroscopic and MR lesions (R (2) = 0.63)-were achieved with TE at 7 ms. The same TE value also gave the best image quality with healthy volunteers.
  
  
  CONCLUSIONS
  Instrument guidance and PRF-based thermometry of PLDD in the lumbar spine are feasible and accurate. Open 1.0 T MR imaging with fast spin-echo and GRE sequence designs may render laser discectomies more effective and controllable.
authors.affiliation: Department of Radiology, Charité, Humboldt-University Medical School, Charitéplatz 1, 10117, Berlin, Germany, florian.streitparth@charite.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Streitparth
authors.forename: Thula
authors.initials: T
authors.lastname: Walter
authors.forename: Uta
authors.initials: U
authors.lastname: Wonneberger
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schnackenburg
authors.forename: Carsten M
authors.initials: CM
authors.lastname: Philipp
authors.forename: Federico
authors.initials: F
authors.lastname: Collettini
authors.forename: Ulf K M
authors.initials: UK
authors.lastname: Teichgräber
authors.forename: Bernhard
authors.initials: B
authors.lastname: Gebauer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019299:Decompression, Surgical; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007403:Intervertebral Disc / Q000601:surgery*; D053685:Laser Therapy / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D053783:Magnetic Resonance Imaging, Interventional; D008297:Male; D008875:Middle Aged; D062125:Thermometry / Q000379:methods*; D016896:Treatment Outcome